In recent years, as one sphere of approaches to environmental problems, the development of low-emission vehicles has been progressed, and one of the vehicles is a fuel cell vehicle including a fuel cell system as a car-mounted power source. The fuel cell system is an energy conversion system for supplying a reactant gas to a membrane-electrode assembly to cause an electrochemical reaction, thereby converting chemical energy into electric energy. In each assembly, an anode pole is arranged on one face of an electrolytic film, and a cathode pole is arranged on the other face thereof. Above all, a solid polymer electrolyte type fuel cell system in which a solid polymer film is used as an electrolyte can easily be made compact at a low cost, and additionally it has a high output density. In consequence, the use application of the system as the car-mounted power source is expected.
In a gas channel of a fuel cell stack, formed water generated by the electrochemical reaction of the reactant gas, humidification water for humidifying the reactant gas and the like remain. If the power generation is stopped while leaving this remaining water, the remaining water freezes in an environment at a low temperature, the diffusion of the reactant gas to the membrane-electrode assembly is prevented, and low-temperature starting properties lower.
In view of such a problem, heretofore, when the power generation is stopped, removal processing is performed to drive an air compressor by the power of an accumulator device, thereby discharging moisture remaining in the gas channel of the fuel cell stack. In Japanese Patent Application Laid-Open No. 2003-297399, a method is suggested which estimates the amount of the water remaining in the fuel cell stack to increase a removal time, as the amount of the remaining water is large.
[Patent Document 1] Japanese Patent Application Laid-Open No. 2003-297399